This invention relates to electrical energy power supplies and, more particularly, to battery power supplies of flat configuration.
Batteries formed having a flat, multicell configuration have been recognized as having considerable utility as a power source for advanced, consumer and industrial products. For instance when efficiently designed and fabricated, the power source may exhibit a relatively low internal impedance as well as a relatively high current output capacity. These desirable powering characteristics, when coupled with a generally flat geometric configuration, ideally lend such power supplies to a use in complement with compact but sophisticated electronically controlled instruments and devices.
As an example of such a union of components, flat primary batteries have been combined with the photographic film packs employed exclusively in a photographic camera sold by Polaroid Corporation of Cambridge, Mass., U.S.A., under the trademark "SX-70". Described, for instance, in U.S. Pat. Nos. 3,705,542; 3,543,662; 3,543,663; and 3,595,661, the film packs are formed comprising a disposable cassette structure containing a dark slide for covering an exposure station in a forward wall thereof, a stack of individual "self-developing" film units positioned behind the dark slide, a spring platen for urging the film units toward the forward wall to position the uppermost one of the film units in the stack at the exposure station and a flat battery positioned opposite to the platen having adjacent terminal surfaces of opposed polarity which are accessible from the rearward wall of the cassette. Thus configured, the film pack is ideally suited as a component within a photographic system incorporating a highly automated camera of complementing compact configuration. Such a camera may include integrated solid state control circuits as detailed in U.S. Pat. No. 3,774,516 which serve a myriad of functions including the control of tractive electromagnetic drives as described, inter alia, in U.S. Pat. Nos. 3,791,278; 3,750,543; 3,805,204; and 3,820,128. Additionally, the power supply provided the camera permits a utilization of dynamoelectric motor drives and the like as disclosed, for instance, in U.S. Pat. Nos. 3,811,081 and 3,731,608.
For practical utilization, the flat battery structures should be capable of exhibiting efficient performance characteristics without the external application of compressive forces. Alternatives to otherwise necessary compression deriving techniques generally have looked to the incorporation of adhesives, particularly between particulate active electrode materials and current collector surfaces. For instance, in U.S. Pat. No. 3,770,504 particulate electrode material for association with a carbon impregnated polymeric current collector surface is provided with adhesives which generally are insulative in character. The resultant "patch-type" electrode structures typically are performed upon the collector surfaces prior to battery manufacture. These assemblies subsequently are combined in combination with gel electrolyte material and the like to form laminar pile or battery assemblies in continuous web fashion. Desired adhesion of the electrode materials with the collector surfaces, while providing necessary association therebetween, tends to derogate the efficiency thereof inasmuch as chemical activity of the battery necessarily is hindered by the adhesive lattice within which the electrode particles are embedded.
A flat battery structure from which considerably enhanced current drain capacities are available is described in copending application of S. A. Buckler, Ser. No. 495,681, filed Aug. 8, 1974, entitled "Flat Battery" (now abandoned) and assigned in common herewith. This battery includes both positive and negative active components in an aqueous slurry form as particulate dispersions with electrolyte and a hydrophilic polymeric binder or dispersant. The electrode particles within the slurry are present in a concentration per unit area which is effective to provide an electrically conductive dispersion and, in consequence of the higher surface availability of electrode materials within the electrochemical system, batteries of a desirably broad range of current capacities are readily designed and manufactured. For instance, one such manufacturing technique, described in copending U.S. application for U.S. patent by O. E. Wolff, Ser. No. 514,458, filed October 15, 1974 and entitled "Method of Forming A Slurry Battery Cell," (now abandoned in favor of a continuation-in-part thereof, Ser. No. 694,026 filed June, 7, 1976) also assigned in common herewith, describes that the slurry battery structures may be formed in situ as a step in fabrication of a laminar pile assembly.
In a copending application for U.S. Patent, Ser. No. 495,628, filed Aug. 8, 1974, by E. H. Land, entitled "Flat Battery" (now abandoned in favor of a continuation-in-part thereof, Ser. No. 647,590 filed Jan. 8, 1976, now U.S. Pat. No. 4,007,472 issued Feb. 8, 1977) and assigned in common herewith, another flat battery structure of enhanced output capacity is described as incorporating a laminar cell structure having a planar cathode assembly including a current collector carrying on one surface, in order, a first cathode mix comprising a particulate dispersion of cathode mix particles in a binder matrix and a second cathode mix comprising a particulate dispersion of cathode mix particles with hydrophilic binder disposed within aqueous electrolyte, i.e., in slurry form. In this hybrid form of slurry electrode structure, a highly desired improved shelf-life characteristic is evidenced in combination with the noted advantageous higher output capacity.
As may be evidenced from the foregoing, highly desirable in the flat battery field is a structure which enjoys the considerably enhanced fabricability and output capacity of a slurry type electrode system as well as evidences an enhanced interaction between active electrode material and associated collector surface. Where such association is available, improved shelf life, output capacity and fabricability characteristics are realized.